For the uneducated, please explain Tish’ah Be/Av. Thanks.
The blackest day in the Jewish calendar (today), on which both temples were destroyed, the Bar Kokhba' revolt defeated at Betar, the Talmuds burned in medieval France, the Jews expelled from Medieval England and from Spain and Portugal (1492), World War I began, etc.
It was the night of Tish`ah Be'Av when the Israelites in wept upon receiving the report of the twelve spies (Numbers 13), so G-d decreed that since they wept that night for no reason He would make that night a night of true tragedy throughout Jewish history.